package demo5;

import javax.swing.tree.TreeNode;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: liangyuanzhang
 * Date: 2025-4-28
 * Time: 0:41
 */
public class Test {
    public int preIndex;
    public TreeNode buildTree(int[] preorder, int[] inorder) {
        return buildTreeChild(preorder,inorder,0,inorder.length-1);
    }

    public TreeNode buildTreeChild(int[] preorder, int[] inorder, int inbegin, int inend) {
        //这种情况下 表明 当前root 没有子树了
        if (inbegin > inend) {
            return null;
        }
        TreeNode root = new TreeNode(preorder[preIndex]);
        int rootIndex = findVal(inorder, inbegin, inend, preorder[preIndex]);
        preIndex++;
        root.left = buildTreeChild(preorder, inorder, inbegin, rootIndex - 1);
        root.right = buildTreeChild(preorder, inorder, rootIndex + 1, inend);
        return root;
    }

    private int findVal(int[] inorder, int inbegin, int inend, int val) {
        for (int i = inbegin; i <= inend; i++) {
            if (inorder[i] == val) {
                return i;
            }
        }
        return -1;
    }
}
